Method for hardening cobalt steel



Patented June 9, 1936 2,043,533 METHOD FOR HARDENING COBALT STEEL Richards H. Harrington, Schenectady, N. Y., assignor to General Electric Company, a corporac tion of New York No Drawing.

Application October 29, 1931,

Serial No. 571,937

4 Claims.

The present invention relates to a method for I hardening alloy steel and more particularly to a 5 5.5% chromium, 1% carbon and the remainder at C. and. then Oil quenched from 950 C. s iron. A composition of this character is disclosed Although a y o e Of these methods will be found in Honda Patent #1338134, Ordinarily, cobalt to p e a it ble degree of primary hardness. steel such as disclosed in the Honda patent may I have found that. the maximum hardness, in c n-- be hardened by heating the steel to a temperature neetion wit t e p s t invention. ay be n of about 950 C. and then quenching in oil. This tained when the cast bars are simply heated to 10 treatment provides a steel which has a hardness ut 9 C- a d qu d i il- A r at v ly of about 62 on' the Rockwell 0 scale. high p m y ardn s tai d by this treat- It is an object of the present invention to inment and a high Secondary helidnleio is ob crease the hardness of cobalt steel by means of an tamed when the Steel is thereafter a d at about additional heat treatment and to provide thereby 50 C. This cycle 05 primary fi li. 15 a steel suitable for use as a high speed metal followed by t specified e e, s m uttin tool, be applied to the forged steel of like compositions. In carrying out the present, invention the 111a A hardness of fibOl-lt 70 on the Rockwell C scale gredients comprising the tool composition are 18 Obtained for t e forged teel- 20 melted preferably in a high frequency furnace What I claim as new and desire to secure by and cast into bars of convenient size. The cast Letters Patent 0f the United States, bars are then given a primary hardness of about 1. The method of hardening steel consisting 62 on the Rockwell C scale by heating to about i substantially of 5% to 60% cobalt, 1% to 10% 950 C. and quenching in oil. molybdenum with the remainder carbon steel con In accordance with the present invention this taining from about .5% to 2% carbon which com- 5% primary hardness isincreased by aging the steel prises quenching the steel from a temperature in a non-reducing atmosphere such as air or of about 950 C. and aging it at about 450 C. to nitrogen at temperatures varying from about 5 0 C. 450" c, to 550 C, The temperature of the steel 2. The method of increasing the hardness of is raised gradually to the aging temperature and te Consisting Substantially f i0 c t maintained at that point for about 1 to about 10 1% to 10% molybden to 10% chromium hours, after which the steel is cooled in air, and the remainder carbon steel containing about The aging process increases the hardness of the .5% to 2% carbon which comprises melting the steel to about 70.5 on the Rockwell C scale. The ingredients compri g the stee heating the Steel 3 resulting product is harder and tougher than high to a temperature of about 950 C. quenching the speed steel heretofore produced and has been Steel and aging it at about 450 C. to 550 C. found to be particularly suitable for use in ma- 3. The method of increasing the hardness of chining copper, -mica insulated commutators, steel consisting substantially of about 36% by phenol condensation products and the like. weight of cobalt about 8% molybdenum. about The quantities of materials employed in manu- 5.5% chromium and about 1% carbon with the facturing the steel may vary within the limits remainder iron, which comprises quenching the indicated in the Honda patent. Generally, the steel from about 950 C. and aging the steel at a alloy will consist mainly of iron and cobalt but temperature within the range of 450 to 550 C. y will contain molybdenum, chromium and carbon 4. The method of increasing the hardness oi in appreciable but minor quantities, the molybsteel containing 5 to cobalt, 1 to 10% molybdenum usually being in excess of the chromium. denum, 0.5 to 10% chromium, the remainder con- Although I have indicated only one method for sisting substantially of carbon steel containing 0.5 obtaining the primary hardness in the present to 2% carbon which comprises quenching the steel alloy, various other well known methods may be from about 950 C. and aging the steel at a tememployed if desired. For example, the primary perature within the range of about 450 to 550 C.

method for hardening cobalt steel containing for example about 36% cobalt, 8% molybdenum,

hardness may be obtained by normalizing the cast bars at about 1150 C. and then quenching at 950 C. or the cast bars may be annealed from 750 C. and then oil quenched from coo" ilk, or the cast bars may be normalized at 1150 C. annealed RICHARDS H. HARRHVGTUN. 

